The present invention relates to a polymeric, thermosetting molding composition which exhibits controlled flow when subjected to elevated molding temperatures and pressures. Broadly speaking, it has been found that a superior molding composition can be produced by preparing epoxide-vinyl ester resinous compositions derived from epoxide resins and having significant quantities of vinyl ester terminal groups (having .alpha.,.beta.ethylenic unsaturation) and significant quantities of epoxide terminal groups, and reacting the epoxide groups with a sufficient quantity of a polyfunctional amine to significantly raise the viscosity of the resulting resinous materials when the latter is subjected to molding temperatures. Incorporated in the compositions may be free-radical initiator catalysts and ethylenically unsaturated monomers, together with such fillers, pigments and the like as may be desired. Exposure of the resulting compositions to pressures at molding temperatures in the range of about 250.degree. F. (about 121.degree. C.-160.degree. C.) causes the compositions to soften and controllably flow within the mold cavities, and culminates in cross-linking or curing of the compositions via the addition reaction through ethylenically unsaturated groups of the resins and monomers.
In one embodiment, the invention relates to an epoxide-vinyl ester resin composition having significant quantities of both epoxide terminal groups and ethylenically unsaturated terminal groups. The resin composition desirably is derived from an epoxide-terminated resin by reaction of a significant portion of the epoxide groups with an organic, desirably monobasic acid having .alpha., .beta., ethylenic unsaturation, the resin retaining a significant quantity of terminal epoxide groups. The composition desirably contains, as a catalyst, a peroxy free-radical initiator such as 2,5-dimethyl-2,5-bis(2-ethylhexanolyperoxy)hexane, t-butyl perbenzoate and 1,1-di-tert.butylperoxy-3,3,5-trimethyl cyclohexane (as a 75% solution), and, desirably, an organic, ethylenically unsaturated monomer such as styrene, the monomer being present in a quantity providing up to about 13, (desirably 0.7 to 13 and most preferably 0.7 to about 7) times the stoichiometric amount of monomer required to react with the ethylenically unsaturated groups of the resin.
In another embodiment, the invention relates to the resinous reaction product of an epoxide-vinyl ester resin having significant quantities of epoxide and ethylenically unsaturated terminal groups, with a polyfunctional amine reactable with epoxide groups of the resin and in sufficient quantity to provide the resulting resin with a viscosity significantly greater than (preferably, at least twice as great as) the viscosity of the epoxide-vinyl ester resin at molding temperatures, the reaction product retaining the reactive ethylenically unsaturated groups. The resinous reaction product desirably also contains a free-radical initiator catalyst such as the peroxy catalyst exemplified above and, desirably, an ethylenically unsaturated monomer such as styrene, in an amount providing up to 13 and preferably from about 0.7 to 7.0 times the amount required for stoichiometric reaction with ethylenically unsaturated groups of the resinous reaction product.
In yet another embodiment, the invention relates to a method for providing a vinyl ester-type molding composition having controlled flow at elevated molding temperatures in the range of 250.degree. F.-320.degree. F. (about 121.degree. C.-160.degree. C.) which comprises reacting an epoxide terminated resin with less than a stoichiometric amount of an organic acid having .alpha.,.beta.ethylenic unsaturation to provide an epoxide-vinyl ester resin having significant quantities of epoxide and ethylenically unsaturated terminal groups. The resulting resin is then reacted, through its epoxide groups, with a reactive polyfunctional amine in sufficient quantity to provide the resinous reaction product with a viscosity at molding temperatures significantly greater than that of the epoxide-vinyl ester resin.
In a further embodiment, the invention relates to a two-part resin system of which the parts are combinable and reactable to provide a moldable, thermosetting composition having controlled flow at molding temperatures. One part compreses an epoxide-vinyl ester resin having significant quantities of both epoxide and ethylenically unsaturated terminal groups, and desirably an ethylenically unsaturated monomer in the range of up to 13 and preferably from 0.7 to 7.0 times the stoichiometric amount required to react with the ethylenically unsaturated groups of the resin. The other part comprises an epoxide-reactive, polyfunctional amine, preferably a tertiary amine, in sufficient quantity to react with epoxide terminal groups of the resin and to provide a resinous reaction product having reactive, ethylenically unsaturated groups and characterized by a viscosity at molding temperatures significantly greater than that of the epoxide-vinyl ester resin.
Although the preferred embodiments employ epoxide-vinyl ester resins having epoxide and vinyl ester groups in the same molecule, an operative embodiment of the invention, which may be preferred for some uses, may employ an epoxide vinyl ester resinous composition in which the epoxide and vinyl ester groups are supplied by different molecular species.